Application of orthogonal functions fitting to the exploration of massive sulphide deposits in Ashele, Xinjiang.

The large Cu-rich deposit is a typical volcanogenic massive sulphide. Thick, large and lenticular orebodies display the stratabound character and there are appreciable density differences between orebodies and country rocks. Ground geophysical methods, especially the gravity method, have proved the most effective for the reconnaissance of hidden massive sulphides. However, the Ashele district is characterised by complex geological structures and the gravity anomalies are usually masked. To solve this problem, orthogonal functions fitted to the Bouguer anomaly were selected for the district which then separated the local gravity anomalies due to the ore horizons from the measured anomalies. A tectono-metallogenic belt was successfully outlined, ore district structures determined, eleven local gravity anomalies were found and the ore prospecting area was charted. It was found that the minimum density of the ores was higher than the maximum density of the country rocks. This shows that gravity anomalies will appear where the ores are.
The large Cu-rich deposit is a typical volcanogenic massive sulphide. Thick, large and lenticular orebodies display the stratabound character and there are appreciable density differences between orebodies and country rocks. Ground geophysical methods, especially the gravity method, have proved the most effective for the reconnaissance of hidden massive sulphides. However, the Ashele district is characterised by complex geological structures and the gravity anomalies are usually masked. To solve this problem, orthogonal functions fitted to the Bouguer anomaly were selected for the district which then separated the local gravity anomalies due to the ore horizons from the measured anomalies. A tectono-metallogenic belt was successfully outlined, ore district structures determined, eleven local gravity anomalies were found and the ore prospecting area was charted. It was found that the minimum density of the ores was higher than the maximum density of the country rocks. This shows that gravity anomalies will appear where the ores are.